There is a two measure harmonic pattern that is in each key. It's in measures 82-83, 84-85, and 88-89. The two beat sequential pattern is repeated many times throughout measures 80-89. the first two measures of the sequence goes down by a half step then after that it looks as if the sequence goes down by way of falling thirds.

The two sequences are layered on top of each other in this excerpt. You could say that the shorter melodic sequence acts as a way to connect the longer harmonic sequence. the melodic sequences also provides a link between keys by introducing or reintroducing notes of the upcoming key within the sequence.